Vivariums house a number of animals, typically test animals, such as rats or mice, in a number of cages, often a large number. Vivariums are expensive and time consuming to build. Sterility and a well-controlled environment require expensive, specialized systems, including those to manage airflow, temperature, and the ingress and egress of personnel and equipment. Typically, it is not possible to expand an operating vivarium or perform major maintenance on a vivarium while it is operating. Prior art vivariums are not modular.